The online version of this article (doi:10.1186/1475-2875-11-168) contains supplementary material, which is available to authorized users.
The authors declare that they have no competing interests.
AHO participated in conception and designing of the study, carried out the molecular genetic studies, the luciferase reporter gene assay, performed data analysis, interpretation, and drafted the manuscript; YM participated in conception and designing of the study, data analysis, interpretation and revising the manuscript critically; YA participated in designing of the study, data collection and analysis; HS assisted during the luciferase reporter gene assay experiment; MFO and BDA participated in designing of the study, and data collection; SMN participated in designing of the study and revising manuscript critically; KM participated in designing of the study and data analysis; KH participated in conception and designing of the study, data analysis, interpretation, revising manuscript critically and gave final approval of the version to be published. All authors read and approved the final manuscript.
In areas mesoendemic for malaria transmission, symptomatic individuals play a significant role as reservoirs for malaria infection. Understanding the pathogenesis of symptomatic malaria is important in devising tools for augmenting malaria control. In this study, the effect of TLR9 polymorphisms on susceptibility to symptomatic malaria was investigated among Ghanaian children.
Four hundred and twenty nine (429) healthy Ghanaian children, aged three to eleven years (3–11 years), were enrolled into a cohort study and actively followed up for symptomatic malaria for one year. Four TLR9 single nucleotide polymorphisms (SNPs) namely: rs187084 (C-1486 T), rs5743836(C-1237 T), rs352139 (G + 1174A) and rs352140 (G + 2848A) were genotyped by direct sequencing, and their attributable and relative risks for symptomatic malaria determined. TLR9 haplotypes were inferred using the PHASE software and analysed for the risk of symptomatic malaria. A luciferase assay was performed to investigate whether the TLR9 haplotypes influence TLR9 promoter activity.
The rs352139 GG genotype showed a significantly increased relative risk of 4.8 for symptomatic malaria (P = 0.0024) and a higher mean parasitaemia (P = 0.04). Conversely, the rs352140 GG genotype showed a significantly reduced relative risk of 0.34 (P = 0.048). TLR9 haplotypes analyses showed that TTAG haplotype was significantly associated with reduced relative risk of 0.2 for symptomatic malaria (P = 4×10-6) and a lower mean parasitaemia (0.007), while CTGA haplotype had an increased relative risk of 3.3 (P = 0.005). Functional luciferase reporter gene expression assay revealed that the TTA haplotype had a significantly higher promoter activity than the CCG, CTG and TCG haplotypes.
Taken together, these findings indicate a significant association of TLR9 gene polymorphisms with symptomatic malaria among Ghanaian children in Dangme-West district.
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- Toll-like receptor 9 (TLR9) polymorphism associated with symptomatic malaria: a cohort study
Ahmeddin H Omar
Michael F Ofori
Bartholomew D Akanmori
Mohammed Nasir Shuaibu
- BioMed Central
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